LONG ISLAND VEGETATION 



199 



morpha intestinalis become such abundant epiphytes as to obscure 

 the Zostera itself. On the rocks in the bottom of the channel the 

 flora is further enriched by Bryopsis plumosa, Dasya elegans, 

 Gracilaria multipartita, and Rhahdonia tenera. 



The future history of this tidal creek phase of the Eel Grass 

 Formation is easy to predict. The continual aggradation of the 

 salt marsh by sedimentation and the accumulation of vegetable 

 debris diminishes the quantity of water which must flow in and 

 out through the channel at each tide. This means decreased 

 erosion and finally the inability to prevent the choking up of th 

 channel by Zostera. This stage has already been reached toward 

 the upper end of the creek. With the choking up of the channel 

 comes the gradual encroachment of the pioneer plant of the salt 

 marsh, Spartina cynosur aides. Fiicus, especially the form with 

 the spiralh' twisted thalli commonly forms the principal associate 

 of the Spartina. The further development will be discussed under 

 the salt marsh. The decrease in quantity of water in the late 

 stages results in decreased exposure to the air in the marsh, in- 

 creased temperature of the outflowing water during the summer, 

 decreased rate of flow, and an increasing tendency of the channel 

 to go dry between tides. 



A third phase of the Eel Grass Formation is to be seen in the 

 mud flats at the inner end of Cold Spring Harbor. These flats are 

 exposed to the air in large part at each low tide so that physio- 

 graphicalh^ they partly belong to the lower beach. But they need 

 to be mentioned in this connection as the last remnant of this 

 formation. They offer conditions unsuited for its best develop- 

 ment and at the same time the depth of water at high tide is suffi- 

 cient to prevent the immediate coming in of Spartina. But 

 aggradation is comparatively rapid and if present tendencies are 

 not interfered with the salt reed grass will take possession. The 

 channel which connects this mud flat with the outer harbor sup- 

 ports some of the red algae already mentioned in connection with 

 tidal creeks, but the number and variety is subject to great varia- 

 tion in successive years. ^ 



Johnson, D. S. and York, H. H. The Relation of Plants to Tide Levels. Cold 

 Spring Harbor Monograph (will contain a detailed description of this inner harbor 

 by tide levels). 



